This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Action potential initiation, modulation, and propagation depend on high densities of voltage-gated ion channels clustered at axon initial segments (AIS) and nodes of Ranvier. The mechanisms that underlie their assembly and maintenance are important to understand since any therapeutic strategy aimed at nervous systems repair or recovery must consider the preservation or reassembly of these domains. One impediment to elucidating these mechanisms is the relatively small number of proteins that have been identified at these important sites. In this project, we will utilize laser capture micro dissection to micro dissect the AIS, followed by mass spectrometry to perform a molecular dissection of the axon initial segment. With newly identified proteins in hand, we will then use a variety of biochemical, cell biological, and genetic methods to determine their functions.